No. I think it's thick and durable. I haven't used it yet but I don't imagine your knew would sink in at all. I'm actually going to use it to our under my daughter because she kicks like crazy once I take her out if the bath and I think it will prevent her from hurting her ankles on the counter as I dry her. Hope that helps
It is soft to your knees, very comfortable. I use it in my workouts, to do "modified" push ups, for instance. It is sturdy to withstand the weight, pressure and common use. But soft enough to be comfortable to kneel on.